Aspects of the present disclosure relate to a document holder, an image scanner including the document holder, and an image forming apparatus including the document holder.
Some current image scanners include an automatic document feeder (hereinafter abbreviated as ADF), when documents to be fed are placed on a document tray, the placed documents are generally positioned using document guides.
More specifically, when ADFs include document guides that are movable such that their positions can be changed in accordance with the document width. For example, the positions of the documents guides may be adjustable by sliding the document guides in a direction (hereinafter also referred to as document width direction) perpendicular to the direction in which documents are fed by the ADF.
The pair of document guides, with one guide disposed on each side in the document width direction, are provided with racks sliding together with the document guides and a pinion meshing with both of the racks. These form an interlock mechanism that, when one of the document guides is slid, cause the other document guide to also slide in synchronization therewith.
In some arrangements, an ADF is mounted on a flatbed image scanner (hereinafter, flatbed will be abbreviated as FB). This type of FB image scanner generally includes a main body portion with upper surface configured to serve as a placing surface on which a document can be placed, and to scan an image from the document placed on the placing surface while moving an image sensor along the placing surface. Above the main body portion, an opening and closing portion is provided that is openable and closable relative to the main body portion. When the opening and closing portion is closed, the opening and closing portion functions as a cover that covers the placing surface.
According to some configurations, the ADF may be incorporated in the opening and closing portion. When documents are fed by the ADF with the image sensor at a predetermined scanning position, the documents pass through a position facing the image sensor, and images can be scanned from the documents with the image sensor.
In the case where the above-described ADF is incorporated in an opening and closing portion, the sliding direction of the document guides may become inclined relative to the horizontal plane when the opening and closing portion is opened, depending on the relationship between the center of rotation of the opening and closing portion and the sliding direction of the document guides.
For example, in the case where the opening and closing portion rotates about an axis extending in a direction perpendicular to the sliding direction of the document guides, and when the opening and closing portion is opened, one of the document guides becomes higher than the other document guide. This situation also results in the sliding direction of the document guides becoming inclined relative to the horizontal plane.
If documents are placed on the document tray at this time, the load of the documents acts on the lower document guide. For this reason, if the operating load required to slide the document guides is too small, the load of the documents causes the document guides to slide. As a result, the documents slide down from the proper position together with the lower document guide.
Such a problem can be avoided by using a structure in which a large operating load is required to slide the document guides. In this case, the document guides do not slide easily when they are subjected to a small load.
However, if the operating load required to slide the document guides is too large, a large operating load is required when the user operates the document guides to slide them, and therefore the operability of the document guides is lowered.